WebBrowser控件而getElement通过ID [英] WebBrowser Control and GetElement by ID
问题描述
我使用Visual C＃的WinForms来控制WebBrowser对象。
I am using Visual C# Winforms to control a WebBrowser object.
我特别想用WebBrowser.Document.GetObjectByID（身份识别码）。样式设置一个对象，它是加载到WebBrowser对象的文档的一部分的风格。
Specifically I want to use WebBrowser.Document.GetObjectByID("myid").Style to set the style of an object that is part of the document loaded into the WebBrowser object.
我想有按钮在WinForm切换标题的风格从显示：无到显示：块;文本对齐：中间。
这是我在做什么：
I want to have button on the WinForm toggle the Style of a heading from "display:none" to "display:block;text-align:middle". This is what I am doing:
private void frmView_Load(object sender, EventArgs e)
{
string question = "How many cows?";
string answer = "5 cows";
webBrowser1.Navigate("about:blank");
webBrowser1.Document.OpenNew(false);
webBrowser1.Document.Write("<html><body><div id='question'><h1>");
webBrowser1.Document.Write(question);
webBrowser1.Document.Write("</h1></div><div id='answer'><h2>");
webBrowser1.Document.Write(answer);
webBrowser1.Document.Write("</h2></div></body></html>");
webBrowser1.Refresh();
webBrowser1.Document.GetElementById("answer").Style = "display:none;";
//if I do a breakpoint here, I get the Style = "DISPLAY:NONE"
btnAnswer.Visible = true;
btnNext.Visible = true;
}
private void btnAnswer_Click(object sender, EventArgs e)
{
//if this is the first time ran, doing a breakpoint here will
//show Style to be NULL
webBrowser1.Document.GetElementById("answer").Style = "display:block;text-align:center";
//now the Style is properly set, and will remain that way, even after this function returns}
请注意，我能够控制的btnAnswer_Click方法Style属性，但不能与frmView_Load方法。我知道我可以只是把样式信息到div标签，当我创建它（这样做的工作），但为什么不code以上工作？
Note that I am able to control the Style property with the btnAnswer_Click method, but not with the frmView_Load method. I know I can just put the style info into div tag when I create it (this does work), but why doesn't the code above work?
更新：
我发现了一些可能在正确的方向走了。如果我称之为 webBrowser1.Update（）在后 WebBrowser1.Navigate时任一点（关于：空白）一切frmView_Load工作。不幸的是，任何企图改变后frmView_Load出口将失败的文档。他们不仅将失败，但frmView_Load返回后webBrowser1.Document将被设置为NULL莫名其妙。
任何人都可以提供一些线索对这个控制是如何工作的？
Update:
I found something that may be going in the right direction. If I call webBrowser1.Update() at any point after webBrowser1.Navigate("about:blank") everything in frmView_Load works. Unfortunately, any attempts to change the document after frmView_Load exits will fail. Not only will they fail, but after frmView_Load returns webBrowser1.Document will be set to NULL somehow.
Can anyone shed some light on how this control is supposed to work?
推荐答案
检讨WebBrowser控件MS文档后，我意识到，一切浏览器是异步的。话虽如此，这意味着我必须为了确保这些属性已经设置设置属性来阻止我的控制线程。
After reviewing the MS Documentation on the WebBrowser control, I realize that everything the browser does is asynchronous. Having said that, it means that I have to block my control threads after setting properties in order to ensure those properties have been set.
基本上，我的写到文档不这样做只是因为写函数返回。我必须阻止控制线程，直到文件反映了这些变化，如果我想引用写的内容。 MS建议睡眠循环。下面是我写＆安培;块的功能如下：
Basically, my "write" to the document isn't done just because the "write" function returns. I have to block the control thread till the document reflects those changes if I want to reference the contents of that write. MS recommends a sleep loop. Here's what my write & block function looks like:
private void ChangeDocument(string documentText, double timeout)
{
DateTime startTime = DateTime.Now;
double elapsed = 0;
if (webBrowser1.Document == null)
{
webBrowser1.Navigate("about:blank");
}
webBrowser1.Document.OpenNew(false);
while ((webBrowser1.DocumentText != "") && (elapsed < timeout))
{
Thread.Sleep(50);
elapsed = DateTime.Now.Subtract(startTime).TotalMilliseconds;
}
webBrowser1.Document.Write(documentText);
startTime = DateTime.Now;
elapsed = 0;
while ((webBrowser1.DocumentText != documentText) && (elapsed < timeout))
{
System.Threading.Thread.Sleep(50);
elapsed = DateTime.Now.Subtract(startTime).TotalMilliseconds;
}
}
感谢您的答复大家。
Thanks for your responses everyone.
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